In the early history of power transmission chain, inverted tooth or silent chain was constructed of sets of links connected together at articulating joints by circular pins. Later, the pin was replaced with a two part joint comprising a pin and a rocker having abutting surfaces, one of which is rockable on the other. Various configurations of pins and rockers have been suggested in the prior art. For example, U.S. Pat. No. 3,213,699, describes a pin and rocker joint constructed from pins and rockers which are substantially identical to each other in section. Each pin and rocker taught by the above patent has an arcuate rocking surface, and an arcuate back surface substantially concentric with the rocking surface. When assemblying a chain with such a pin and rocker configuration, it is possible, by rotating a pin rocker through 180.degree., to improperly position it in the link apertures. This may not be detected upon inspection, and leads to early chain failure and improper operation. Because each of these components has only one working surface suitable for rocking engagement with the other when this surface becomes worn, both components must be replaced.
Another problem encountered with the use of the pins and rockers of the above identified patent is that the apertures in the links through which the pins and rockers extend must necessarily have portions with irregularities such as reentrant angles and small radii to properly position the joint elements. This results in high stress concentration in the vicinity of such abnormalities and small radii. Accordingly, the links must be made larger and/or of different shape than they would need be if the stress concentration were reduced.